/dev/shm and /tmp are world writeable; any user can write files there.

There is no 100% way to block these. ModSecurity and CXS can help. However the only way to not have your customers be infected with these is to make them keep their CMS software (joomla, wordpress, etc.) fully updated and with good strong administrative passwords.

You can also set in /usr/local/lib/php.ini the disable_functions setting to disallow exec and other risky php functions. Mine is set something like:

Staff Member

Yes, as quizknows mentioned, the best way to avoid these types of attacks is to make sure your customers use updated versions of their scripts with strong passwords. This might seem like a tedious task, but in the long run it's a good investment of your time compared to the time it might take to handle an account that has been exploited.